Ōtaki reservoirs
We received a $29.3 million contribution from the Crown Fund to help fund water and transport infrastructure to improve resilience and support new homes in Ōtaki. You can read more about this on our A blueprint for Ōtaki page.
This includes building two new reservoirs for Ōtaki. The reservoirs will improve the resilience and firefighting capability of the Ōtaki water supply.
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Artist impression of the Ōtaki Reservoir number 1 with trees near fully grown.
Ōtaki has limited water storage and relies on bores and pumps to supply the community. This system does not meet good practice standards. If a problem occurred with the pumps or the treatment station, then most of Ōtaki would lose their water supply. The new reservoirs will provide 24 hours of water storage.
The new reservoirs will:
- improve the resilience of the Ōtaki water supply
- improve firefighting capability for Ōtaki
- provide water storage for emergencies and times of high demand
- support the significant housing growth planned for Ōtaki
- be more energy efficient.
Seismic design
The reservoirs will be designed to withstand a one-in-2,500-year earthquake, making them some of the strongest structures in the area. During a major earthquake, the tanks are designed to move a small amount. Movement of around 25mm to 100mm can be expected to occur in a 2,500-year earthquake. Designing for some movement results in better seismic performance compared to a reservoir that is totally locked in place. Pipework will include flexible joints to allow for any movement of the tank.
We worked with the community to develop a planting plan to screen the reservoir from homes. 2500 native trees and flaxes have now been planted on the site around the reservoir.
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Ōtaki Reservoir planting plan.
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Pipelines from the new Ōtaki reservoir along Te Manuao Road to the County Road pump station.
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Our reservoir takes shape with all 36 prefabricated wall panels now in place.
Key features
Reservoir number 1 by the numbers:
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5.5 million litres (5,500m3) |
volume of the reservoir |
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35 metres |
diameter of the reservoir |
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6 metres |
depth of water in the reservoir |
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7 metres |
height of the reservoir |
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53 metres |
maximum height of the reservoir above sea level |
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267 |
the number of native trees that will be planted around the reservoir |
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100 years |
reservoir design life (length of time the reservoir can be used with maintenance but without major repair being needed) |
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2,500 years |
reservoir designed to withstand an earthquake of this frequency (making it the strongest structure in the area) |
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4 kilometres |
length of pipes to be installed, made up of 1.8km to convey water from the County Road pump station to the reservoir, 1.8km to carry water from the reservoir back to join the reticulation network at the County Road pump station, and 0.5km of pipes for overflow or flushing from the reservoir to join the stormwater network |
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Expected construction timings for the reservoir |
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Estimated Dates |
Activity |
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October/November 2023 |
Earthworks – clearing the area and building earth bunds to help screen reservoir |
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January |
Trenching from tank site to Te Manuao Road for pipework |
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November 2023–February 2024 |
Ground improvements to provide a strong foundation for the tank |
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February 2024 |
Build concrete pad for reservoir |
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February–June |
Install pipes from reservoir site to County Road pump station |
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March–November 2024 |
Construct tank and control equipment |
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April/May 2024 |
Plant native trees to screen the reservoir and create a natural environment |
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August 2024 - Jan 2025 |
Construct reservoir tank |
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Feb 2025 -April 2025 |
Construct reservoir roof |
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May 2025 |
Fill and calibrate tank |
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June 2025 |
Reservoir fully operational |
Reservoir 2
The second new reservoir for Ōtaki will hold between 0.5 to 1.0 million litres of water. It will serve the area around the Waitohu Plateau (properties above the 25 m contour). The new reservoir will supplement the existing Waitohu Reservoir which is nearing the end of its design life and does not meet modern seismic standards.
As at September 2024, we are investigating a potential site. If the site is viable, we will engage with neighbours who could be impacted.